Pipe junction restrainers and techniques for their assembly have been developed to make fluid-tight connections between two axially-aligned pipe joints, valves, fittings, hydrants or other types of fluid connections. Often these junction restrainers must withstand extraordinarily great pressures associated with water distribution and sewer connections. Segmented or split pipe joint retainer glands are well known and typically are secured together around a pipe section by ears or lugs formed on, or extending radially outwardly from, the gland segments. In addition, because of the forces involved, heavy concrete thrust blocks are often used to minimize movement.
In recent years, it has been the practice of many contractors to employ polyvinyl chloride (PVC) plastic pipe in new construction. Unfortunately, many of the underground sewer and water distribution pipes, fittings and valves still contain cast iron and ductile iron. Since these dissimilar materials cannot be joined by conventional means, such as brazing, soldering or gluing, gland restraining devices have been adapted to provide a fluid-tight connection.
Some current gland restrainer systems designed for PVC piping employ mechanical restrainer connections intermittently disposed around the PVC pipe in a gripping fashion. The gland segments of these devices are then bolted together to complete the connection.
Not all of these restrainer connections, however, can resist the type of sudden thrusts associated with fluid abruptly applied in the axial direction. Some of these arrangements are known to bend and separate at the joints between the segments and often permit the pipes to separate. It is also difficult to mechanically attach to PVC pipe, since the softer polymer tends to deform if radial or compressive stresses are concentrated on its surface. Moreover, PVC is notorious for its slippery surface, thereby frustrating restraining devices which principally rely upon friction and elastomeric gaskets alone.
One popular system currently employed exclusively for plastic pipe connections sold under the trademark CERTA-LOK.TM. VIP and produced by CertainTeed Corporation, Valley Forge, Pennsylvania, provides a restrained joint between. PVC pipe for municipal, fire protection, and other uses. The joint connector uses a series of o-ring seals and internal annular cavities that are filled externally with polymeric dowels after two sections of PVC pipe are inserted into the connector. These dowels also fill matching annular cavities located on the pipe sections to form a restraining mechanical lock that has rated at 150 psi and up. Since the restraining mechanism of the CERTA-LOK.TM. joint connector is uniformly distributed around the PVC pipes, the risk of damaging the plastic side walls by localized stress fracture is minimized. Unfortunately, until now, there has been no similar technique for holding pipe joints of dissimilar materials together.
Accordingly, there remains a need for a mechanical joint gland adapter for permitting the assembly of fluid-type fittings containing multiple materials, such as PVC and cast iron. There also remains a need for providing an inexpensive gland adapter which can be field-assembled quickly without much assembly time.